Earthshots: Satellite Images of Environmental Change

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» Denver, Colorado, USA

Denver has all the classic marks of substantial urban growth over the past few decades. Satellite images reveal expanding residential areas, industrial zones, and new freeways that loop around the metropolitan area. Also visible is one of the largest airport building projects in U.S. history.

False color imaging from Landsat that combines shortwave infrared and near-infrared bands shows growth of the city. Bright green is vegetation, so parks and golf courses are the brightest green; dark green is the forested areas in the Rocky Mountains; and the more mottled green shades are the residential areas of the city. Purple hues represent streets, highways, and other mostly unvegetated infrastructure.

Denver is experiencing post-1950 growth similar to other western cities like Los Angeles, Phoenix, and Dallas. The Denver metropolitan area expanded in urbanized land from 150 square miles in 1950 to 499 square miles in 2000, primarily onto prairie and agricultural lands.

Map of the featured area.

A major development in this time series of images is Denver International Airport. A massive piece of infrastructure, the airport sits on 34,000 acres of land, making it the second largest airport in the world. Located 23 miles northeast of downtown Denver, the airport was the fifth busiest in the U.S. in 2017.

Its footprint on the landscape is impressive, and the airport even has room to expand. Prepared for plenty of future growth, there is enough space to expand it from 6 runways to 12.

Construction began in 1989, and the disturbance to the former farm and range land can be seen in the Landsat image from 1990. The transformation from agriculture to developed land use was complete soon after, and the airport’s first flight took off in 1995.

That first year, the Denver airport serviced 31 million passengers. In 2018, 64.5 million passengers traveled through the airport.

The runway layout was planned to be as efficient as possible. None of the runways intersect. And there is enough space between them to accommodate simultaneous landings even in poor weather. This plan reduces delays and minimizes the risk for aircraft traffic jams.

Five of the runways are 12,000 feet long. The sixth was a more recent addition. Brought into service in September 2003, this runway is 16,000 feet long and 200 feet wide. That’s about 2 Landsat pixels wide, but it shows up clearly in the imagery because it’s 162 Landsat pixels long. It’s the longest commercial runway in North America.

The extra length is needed in Denver’s high elevation. Particularly for departures, larger, heavier planes need the additional space to get off the ground.

Stapleton Airport near downtown Denver served the city since 1929. By the 1980s, it was becoming overburdened and could no longer meet the needs of the growing city. Surrounded by urban development, it could not expand.

Once the new airport went into operation 1995, Stapleton Airport closed. Eventually, all the buildings were demolished—except for one. The control tower still stands. It is now a restaurant, and visitors can enjoy great views of the city at the top of the 12-story tower.

The rest of the land of the airport became part of one of the largest urban redevelopments in the country. Stapleton is now a growing master-planned community with a combination of residential, retail, commercial, and plenty of green space. The residential areas include apartments, townhomes, rowhouses, and larger single-family houses to make it a mixed-income region.

Consisting of 12 neighborhoods, each with its own character, Stapleton’s population grew from 5,000 in 2006 to 28,000 in 2018.

There is a noticeable area of undeveloped land in all that urban growth. Just west of the new airport is open land that is now protected from development.

The former area of farmland and grazing land became a chemical weapons manufacturing facility during World War II. Chemical weapons manufacturing ended in 1969, and Shell Oil Co. began using the facility to produce agricultural chemicals. This continued until 1985.

Referred to as the most contaminated place in America, environmental recovery efforts at the site began in the 1980s and continue today. The area became Rocky Mountain Arsenal National Wildlife Refuge in 1992. The valuable prairie, wetland, and woodland habitat is a sanctuary for bison, deer, bald eagles, owls, and many other species. The refuge reached its current size of 15,000 acres in 2010 and offers visitors fishing, hiking, and wildlife viewing.

USGS aerial photos from 1953 and 1971 show these facilities. Many of the structures are no longer there in recent high-resolution images.

Other urban centers near Denver are also growing quickly. While the population of the Denver metropolitan area increased by 78% between 1990 and 2017, Greeley, about 40 miles north of Denver, increased by 66.5% in the same time period.

In these false color images, residential areas are a mottled green, with streets, highways, and other infrastructure showing up in purple hues. The brightest green spots are golf courses, parks, and other areas that have growing green grass. Bright green circles and rectangles are farm fields. In fact, just about everything that is green in these images away from the mountains is irrigated.

Other expansion seen in these images is the petroleum and natural gas industry. An increased number of bright spots indicates more oil and gas wells.

Population of Greater Denver
Population of Greeley

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